[worklets] Split apart CompositorWorkerThread for sharing with AnimationWorkletThread.

third_party/WebKit/Source/modules/modules.gypi

 {
   'includes': [
     '../core/core_generated.gypi',
     'modules_generated.gypi',
   ],
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
@@ skipping 925 matching lines @@
       'canvas2d/CanvasRenderingContext2DState.h',
       'canvas2d/CanvasStyle.cpp',
       'canvas2d/CanvasStyle.h',
       'canvas2d/ClipList.cpp',
       'canvas2d/ClipList.h',
       'canvas2d/ContextAttributeHelpers.cpp',
       'canvas2d/ContextAttributeHelpers.h',
       'canvas2d/HitRegion.cpp',
       'canvas2d/HitRegion.h',
       'canvas2d/Path2D.h',
+      'compositorworker/AbstractAnimationWorkletThread.cpp',
+      'compositorworker/AbstractAnimationWorkletThread.h',
       'compositorworker/AnimationWorklet.cpp',
       'compositorworker/AnimationWorklet.h',
+      'compositorworker/AnimationWorkletThread.cpp',
+      'compositorworker/AnimationWorkletThread.h',
       'compositorworker/CompositorWorker.cpp',
       'compositorworker/CompositorWorker.h',
       'compositorworker/CompositorWorkerGlobalScope.cpp',
       'compositorworker/CompositorWorkerGlobalScope.h',
       'compositorworker/CompositorWorkerMessagingProxy.cpp',
       'compositorworker/CompositorWorkerMessagingProxy.h',
       'compositorworker/CompositorWorkerThread.cpp',
       'compositorworker/CompositorWorkerThread.h',
       'compositorworker/WindowAnimationWorklet.cpp',
       'compositorworker/WindowAnimationWorklet.h',
@@ skipping 1122 matching lines @@
       'webaudio/ConvolverNodeTest.cpp',
       'webaudio/DynamicsCompressorNodeTest.cpp',
       'webaudio/ScriptProcessorNodeTest.cpp',
       'webaudio/StereoPannerNodeTest.cpp',
       'webdatabase/QuotaTrackerTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }